This invention relates to finned rod sections adapted to be driven through the ground and particularly to the use of such a rod section in placing a driven-type survey monument.
Finned monument rods adapted to be driven through the ground are known. Such rods offer rotational and horizontal stability once in place and are thus particularly appropriate for use as survey monuments. Finned rods can also effectively dissipate heat through their extended fins thereby minimizing the depth affected by surface heating. This is particularly important for stabilizing monuments installed in permafrost. Finned rods, however, are generally more resistant to being driven than cylindrical rods and, of course, cannot be used where they must rotate during installation. Moreover, capping a finned rod at the ground surface can be inhibited by the fins.
Survey monuments which must be driven deep underground or to an indeterminate point of refusal commonly include several sections of rod which are joined as the monument is installed. A particularly useful monument is disclosed by U.S. Pat. No. 4,087,945 to Berntsen et al. The Berntsen et al. monument has cylindrical rods which are joined by threaded connectors incorporated within the cylindrical cross-section of the rods and a barbed penetrating point designed to rotate as it is driven such that the threaded connections are tightened during the driving process. Berntsen et al. also shows a marker cap designed to fit tightly over the monument after it has been fully driven.
Devices incorporating the self-tightening invention disclosed by Berntsen et al. are relatively easy to install. However, such monuments may be subject to tampering. In particular, the uppermost section may be uncoupled by grasping that section at the ground surface and rotating it until the threaded connection is parted. One solution to this problem is disclosed in copending application Ser. No. 534,414, now U.S. Pat. No. 4,502,258, which shows a finned section which may be incorporated into the upper portion of a monument. The fins on the finned section engage the earth to prevent rotation either during installation or upon attempted removal. The finned section also provides horizontal stability to the monument. Moreover, the finned section cooperates with a series of threadedly connected cylindrical rod sections beneath it by resisting the torque imposed on the cylindrical rod sections by a rotating point section and thus aids in tightening the connections between all the sections.
Standard marker caps designed for monuments of standard cross section, particularly cylindrical monuments, cannot be used on the finned sections unless the fins are first severed and the remaining rod is filed down to permit capping. This can prove cumbersome in the field, particularly where the process must be accomplished at or slightly below ground grade.